Changes in locusts diversity, niche and interspecific association at different altitudes in the Ili River basin of China

Species diversity at different altitudes exhibits different variation patterns. In alpine ecosystems, species migration from low to high altitudes has changed the intensity of interspecific competition and association, inevitably adjusting or changing the existing prevention and control objects and strategies. In this context, selecting a typical area to probe the variations in species diversity and interspecific competition and association is imperative. Thus, this study investigated the diversity of locusts and grasshoppers at 400 m intervals in the grasslands at different altitudes in the Ili River basin of China. The responses of locusts (or grasshoppers) diversity, ecological niche, and interspecific association to altitudinal variations were comprehensively analyzed using univariate linear regression and redundancy analysis. The results showed that the diversity of locusts and grasshoppers declined with rising altitude. Average vegetation height and wind velocity significantly affected the diversity of locusts and grasshoppers at altitudes of 1,000–1,400 and 1,400–1,800 m, respectively. The vegetation dominance, aspect, and relative humidity significantly affected the diversity of locusts and grasshoppers at 1,800–2,200 m. Nonetheless, no ecological factor significantly affected the diversity of locusts and grasshoppers at ≤ 1,000 m. Before 1,400 m, the rise in altitude intensified the interspecific competition and tightened interspecific relationships. From 1,400 m, the interspecific competition was weakened, and interspecific relationships were loosened. Calliptamus italicus, Oedaleus decorus, and Calliptamus barbarus were the dominant locust taxa in the Ili River basin, with C. italicus and O. decorus being distributed at multiple altitudes, especially within ≤ 1,800 m. The high population density of C. italicus and O. decorus within this range required intensive monitoring and control. By contrast, Egnatius apicalis and Conophyma sp. were sparsely distributed within the > 1,400 m range, posing challenges in collection of locusts and grasshoppers. Therefore, protective measures should be taken to increase insect diversity in grasslands.